478 LIFE : OUTLINES OF GENERAL BIOLOGY 



Nor is there any proof that muscular movements of the wall 

 of the oviduct itself are able to force the sperms in the effective 

 direction. 



Faced by these dithculties, Prof. G. H. Parker has recently studied 

 the oviduct of the Painted Turtle {Chrysemys picta), and has made 

 an interesting discovery. The oviducts of the turtle possess two 

 systems of cilia: a general system covering most of the interior of 

 the duct and beating away from the ovary (abovarian system), and 

 a restricted narrow tract of cilia extending the length of the duct 

 and beating toward the ovary (proovarian system). Thus sperma- 

 tozoa reach the ovarian end of the oviduct not by their own activity, 

 nor by the muscular movement of the oviduct, nor by the reversal 

 of the ciliary beat in this duct, but by transportation afforded by the 

 proovarian ciliary tract. 



Painted Turtles may seem rather remote, but the next step is, 

 of course, to discover whether there is a double ciliary system in 

 the oviduct of birds and mammals. If the down-current is too strong 

 for spermatozoa to make their way against the stream, then we 

 do not know how the intimate fertilisation is effected in sheep and 

 cattle and horses and poultry. But if Parker's discovery of a narrow 

 tract of proovarian cilia in the turtle is corroborated in mammals 

 and birds, then another obscurity disappears. 



Fertility of a P^emale Mule. -One of the miscellaneous 

 items of incorrect information that the man in the street rarely 

 fails to possess is that "mules are always sterile". For ordinary 

 mules (offspring of male ass and mare) sterility is usual in both 

 sexes, and perhaps universal in males, but it is not invariable in 

 females. Thus in the third part ot Volume V of the Annals of the 

 Natal Museum (1926), Dr. Ernest Warren gives details as to the 

 fertility of a female mule. It was the result of a cross between a 

 jack-donkey and a dark chestnut mare, and came in foal to a 

 hackney stallion. The characters of the foal show a remarkable 

 combination of horse and ass characters, varying from nearly 

 complete dominance of either to perfect blending. 



Stickleback's Eggs. — In regard to many common animals our 

 knowledge of the reproductive processes is still very incomplete, 

 not to say patchy. Thus we cannot even tell a consecutive story of 

 the breeding habits of the Three-s})ined Stickleback {Gasterosteus 

 aculeatus), which occurs commonly in fresh water, but is able to 

 thrive in the sea as well. As is well known, the male makes a little 

 nest of pieces of freshwater plants, fastened by glutinous threads 

 secreted from the kidneys at the breeding season — a good instance 

 of a more or less pathological process that has become in this case 

 normahsed. Several females lay their eggs in one nest, which is 

 valiantly guarded by the one male; and there are eventually 

 120-150 eggs altogether. This is a very small number for 9, fish. 



